The invention relates to a levitation microfurnace apparatus for processing and shaping small bodies where contact with foreign objects or supports could be deleterious. In particular, the invention has application to the processing of minute glass microballoons or microspheres. The microballoon is a thin wall glass structure such as used in the processing fuel in laser fusion. The microballoon is filled with heavy hydrogen cryogenically condensed as a thin layer on the interior of the walls. It is then bombarded with energy focused from a laser. The glass material then vaporizes and the hydrogen contained therein is driven to the center by inertial reaction and compressed to a very dense and very hot plasma material resulting in fusion of the hydrogen.
Glass microballoons (GMBs) which are used to contain the fuel must be precisely spherical and have uniform wall thickness. Those obtainable commercially are only rarely of the required degree of perfection. Sorting them out from the accompanying imperfect GMBs is a major task.
It is thought that the imperfect GMBs might be brought to any degree of geometric perfection by remelting, reprocessing and recooling, all the time maintaining them in a levitated state, out of contact with solid or liquid objects. Alternatively, this containerless type of processing might be applied to the initial formation of GMBs from porous glass frit or other suitable precursor materials, as well as to their reprocessing.
Accordingly, apparatus for levitating the microballoons in a microfurnace so that their formation may be accurately controlled to provide a more perfectly and uniformly formed balloon is a problem to which considerable attention need be given.
In order to form GMBs of large diameters such as up to one centimeter, it is necessary to process them in a low or zero gravity condition such as in space. While apparatus is well known for levitating a specimen of material in a gravitational field by opposed field gradients of electromagnetic, acoustic or gas inertial origin, these apparatus are not entirely suitable for levitating a microsphere in a low gravity environment, where accelerations are typically variable, not only with respect to magnitude but direction as well. When positioning and levitation of a GMB in an orthogonal triaxial coordinate system is necessary such as in processing the GMB in space, the problem of rapid and accurate control of restoring forces to neutralize unwanted extraneous accelerations becomes particularly acute.
One well known method of levitation involves a collimated flow of a number of equispaced equivelocity streams of gas or liquid impinging upon a GMB or other small body in such a way as to counter and neutralize the net force vector tending to displace the body from a preferred position. The device whence these streams issue is commonly called a collimated hole structure (CHS). The depth of the CHS holes in relation to their diameter, their aspect ratio, influences the persistence of the collimation and other levitating properties of the issuing streams. The higher the aspect ratio the greater the persistence.
Due to the fact that the holes have been formed heretofore by drilling, they have been of limited aspect ratio as well as being circular.
A need also exists for apparatus for preparing solid particles of materials such as novel glasses under conditions enabling a quick quench and avoiding contact with a container.